Assessing the Impact of Green Infrastructure on Urban Flood Mitigation Effectiveness

Thesis Abstract

Urban flooding has become an increasingly severe challenge in rapidly expanding cities, driven by climate change, urbanization, and inadequate traditional drainage systems. Conventional flood management approaches often fall short of addressing the complex interactions between hydrological processes and urban land use, necessitating innovative, sustainable solutions such as green infrastructure (GI). This study aims to empirically assess the impact of green infrastructure interventions on urban flood mitigation effectiveness, with specific objectives to evaluate the extent of flood reduction attributable to GI installations, analyze the spatial distribution of flood mitigation benefits, and develop a model for predicting flood reduction outcomes based on GI characteristics. The research employs a mixed-methods approach, integrating quantitative and qualitative data collection techniques within a case study framework. The study population comprises urban local governments, civil engineers, and residents in three metropolitan districts with varied levels of green infrastructure implementation. A stratified random sampling technique is employed, with a sample size of 150 households surveyed through structured questionnaires to capture perceptions and experiences of flooding, and 30 key informant interviews with urban planners and environmental engineers to gather expert insights. Additionally, spatial data on flood events and GI installations are collected through remote sensing and Geographic Information Systems (GIS). Hydrological data, including rainfall records and flood extents over a five-year period, are obtained from municipal agencies. Data analysis involves both descriptive and inferential techniques. Descriptive statistics summarize flood occurrence and residents’ perceptions, while multiple regression analysis determines the relationship between GI features (e.g., green roofs, permeable pavements, rain gardens) and flood attenuation. Geospatial analysis using GIS overlays identifies hotspots and the spatial correlation between GI presence and flood reduction outcomes. The study further applies the Diffusion of Innovations Theory and the Sustainable Urban Drainage Systems (SUDS) framework to interpret the adoption and functional performance of green infrastructure. Quantitative data are analyzed with SPSS, employing regression diagnostics to validate model assumptions, while thematic analysis is used to interpret qualitative interview data. Expected findings indicate that districts with higher densities of GI installations show statistically significant reductions in flood frequency and severity, with regression models explaining up to 65% of the variance in flood mitigation outcomes. The spatial analysis is anticipated to reveal that strategically placed GI features effectively reduce flood plumes and protect vulnerable neighborhoods. The study predicts that perceptions of flood resilience among residents correlate positively with the extent of GI adoption, while technical evaluations demonstrate that certain types of GI—particularly permeable pavements and rain gardens—are most effective in stormwater runoff reduction. This research contributes to existing knowledge by providing empirical evidence on the quantitative impact of specific green infrastructure measures on urban flood mitigation, filling notable gaps concerning spatial effectiveness and community perception. The developed predictive model serves as a decision-support tool for urban planners and policymakers, facilitating optimized deployment of GI based on site-specific factors. The main conclusion emphasizes that green infrastructure significantly enhances urban flood resilience when appropriately designed and strategically implemented. Recommendations include integrating GI into urban planning policies, strengthening maintenance programs, and fostering community participation to ensure long-term sustainability. The study advocates further research into the economic valuation of GI benefits and long-term performance monitoring, positioning green infrastructure as a cornerstone of sustainable urban flood management strategies.